Long piston cores taken from the subsurface of two mountain lakes of the eastern Swiss Alps recovered sediments, which overlie the Flims rockslide deposits. These sediments provide new information on the chronology of the largest known Alpine rockslide and can be used to reconstruct the post landslide environmental evolution. The oldest 14C date of the lake sediments yields a minimum age of the rockslide at 9660–9430 cal. yr BP. In addition, the dating of a wood fragment contained in the rockslide deposits directly below the lake sediments shows a maximum age of 9480–9120 cal. yr BP. The overlap of the maximum and minimum ages, 9480–9430 cal. yr BP, approximates the age of the Flims rockslide. This early Holocene range coincides with a period of higher frequency of large mass movements observed in the Alps, which could be related to climatic changes.